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# ZCO 2019 Discussion

 1 I just hope the cutoff is 15. Can anyone tell me the solution for the first problem? Some where saying using mergesort... Please post your solution for the first problem if anyone solved it fully. code not needed. thanks. answered 02 Dec '18, 17:28 617●7 accept rate: 10%
 1 The logic is pretty simple. Construct two arrays of pair of integers, L and R. In the first position of each element l of L we put in the value l we receive and in the second position, we put in the index. Create a similar array for R. Now sort the array L in decreasing order, and R in increasing order. The score of the i-th person would be the sum of the positions of its corresponding l in L and its corresponding r in R. For example, if $n = 3$, and the l and r values are $$(10, 20), (13, 15), (14, 16)$$ The $L$ and $R$ would be, after sorting, $$L: (14, 2), (13, 1), (10, 0)$$ $$R: (15, 1), (16, 2), (20, 0)$$ Now, $\text{score}[0] = 2 + 2 = 4$, $\text{score}1 = 0 + 1$, $\text{score}[2] = 1 + 0$. Though sadly I was getting WA in the test itself, I have no idea why. My logic is sound. So, I just wrote a quick brute-force solution and got 15. :/ answered 02 Dec '18, 18:14 4★islingr 51●3 accept rate: 0%
 0 Is there an ICO WhatsApp group?! I didn't know about this, could you please upload the group link. answered 02 Dec '18, 14:27 1●1 accept rate: 0%
 0 How did you do the first problem(singing competition)? I did it with brute force, and it was partially accepted. answered 02 Dec '18, 15:24 1★jagoshom 1 accept rate: 0%
 0 @jagoshom I got a 40 point solution. What I did was visualise the ranges on a straight line.Since there can't be any draws the pair with the lowest lower range should have the highest upper range as well.So I stored the ranges in a vector of pairs and sorted the vector. The ans for the ith is 2*(n-i-1). Then I undid the sorting. This clears the second subtask. Someone help me with the 100 point solution please. answered 02 Dec '18, 16:03 2★bdyutish 1●1 accept rate: 0% Well, as far as i heard the first problem, basically it was for each range, count total number of ranges lying totally inside it and number of ranges partially overlapping with it. Both can be solved quite easily using merge sort trees or persistance or any other 2D DataStructure of your choice. That would have made this a blind implementation problem. the intended solution is probably using some binary searches, using which u can determine how many ranges are outside ur boundary and how many are inside. PS: work out the details urself. (02 Dec '18, 17:26)
 0 I did a brute force for the 15pt one, for the 40pt one I did the sorting thing but I did not get the right answer because I was not able to output the answer in the original order.How did you overcome this problem? answered 02 Dec '18, 16:10 1●1 accept rate: 0%
 0 What was the method for the first one? answered 02 Dec '18, 16:11 1●1 accept rate: 0%
 0 I had hell of a time figuring out the way to undo sorting. I finally kept 1 ordered map where keys were elements and values were all 0. And seperately stored the original order in a vector. I then printed 2*(N-i-1) for each i. answered 02 Dec '18, 16:26 143●8 accept rate: 10%
 0 @kayak your code is difficult to understand since it is uncommented. Just post your logic answered 02 Dec '18, 16:29 1●1 accept rate: 0% You need to watch Baahubali to understand the code properly. (02 Dec '18, 16:34) kayak3★ Damn shouldve known that :o (02 Dec '18, 16:36)
 0 @bdyutish How did you undo the sorting? answered 02 Dec '18, 16:33 1★jagoshom 1 accept rate: 0%
 0 @jagoshom I kept a map of pairs as keys and the original indexes as values.You calculate the ans for the sorted vector and assign the answers to an array in the original location using the map. answered 02 Dec '18, 16:59 2★bdyutish 1●1 accept rate: 0%
 0 Can grp admin pls upload the link to the ICO WhatsApp grp? Also @kristopher , people are uploading their marks in both the spread sheets. Pls copy the data till now, and delete one, else analysis is going to get pretty messed up. answered 02 Dec '18, 18:24 1 accept rate: 0%
 0 Is there any chance the cutoff goes down to 15? answered 02 Dec '18, 18:27 1★mg21 0 accept rate: 0%
 0 When are the results released?Like, any idea? answered 02 Dec '18, 20:21 11●1 accept rate: 0%
 0 Please share the logic for the second one. answered 02 Dec '18, 21:35 1●1 accept rate: 0%
 0 Can someone who has got 100pts in the first question share their logic. answered 02 Dec '18, 21:37 1●1 accept rate: 0%
 0 @mg21 it is most probably not going to be 15 since almost anyone could get 15 answered 02 Dec '18, 21:44 1●1 accept rate: 0%
 0 For the second DP problem there are few basic observations. 1) We always put an integer because it will always increase the answer. 2) The answer can either be the maximum length of UpDown subsegment already present+1 ( put any integer at last in the subsegment) or it can be combination of 2 subsegments which are just separated by 1 element which doesn't obey the property. We can make the "bad" element "good" by inserting an integer beside it. Let $dp1[i]$ = maximum length of UpDown subsegment ending at index $i$ Let $dp2[i]$ = maximum length of UpDown subsegment starting at index $i$ Now all that is left is to go through each index and find maximum value of $dp1[i]+dp2[i]$ . We can calculate DP and do this in $O(n)$ with very small constant factor. P.S. I may have missed some details and it is left as an exercise for the reader :P answered 03 Dec '18, 08:03 178●5 accept rate: 11%
 0 Is there any 11th student here who is interested in making a WhatsApp group to prepare for next year's ZCO? answered 03 Dec '18, 18:05 1●1 accept rate: 0%
 0 Any idea when the results are coming out? answered 03 Dec '18, 18:06 1●1 accept rate: 0%
 0 The results are probably gonna be out by Monday i.e,10/12/2018(seeing from previous trends of announcing results ,that is) . Btw ,did anyone properly notice the time limit for the questions? It was 2 seconds .Even a brute Force approach should have worked in c++ and other languages (Java - twice the time limit and python -4 times I guess),according to using just 10^7 ooperations per seconds . answered 08 Dec '18, 12:40 21●2 accept rate: 0%
 0 The results have been probably declared. I received a mail from CodeChef, stating that all students with a score >= 40 have qualified for INOI 2019. Cheers! Arnav. answered 13 Dec '18, 11:27 143●8 accept rate: 10%
 0 I was getting runtime error (SIGSEGV) for my brute force code for Singing Tournament, I don't know the reason behind it. My code - https://ideone.com/Gb5ezB , Please Help. answered 16 Dec '18, 13:28 1●1 accept rate: 0%
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question asked: 01 Dec '18, 19:36

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last updated: 16 Dec '18, 13:29